Reaction vessel having internal recycle means

ABSTRACT

A REACTION VESSEL WHICH IS A VESSEL DIVIDED BY A PARTITION INTO TWO ZONES WHICH INTERCOMMUNICATE ABOVE AND BELOW THE PARTITION. GAS INTRODUCED INTO THE LOWER PART OF ONE OF THE ZONES TO CREATE A DENSITY DIFFERENCE BETWEEN THE LIQUID CONTENTS OF THE TWO ZONES AND CAUSE THE LIQUID TO CIRCULATE. THE PARTITION HAS A HEAD WHICH IS A PLURALITY OF CHANNELS PROJECTING INTO ONE OF THE ZONES, TO ASSIST IN SEPARATION OF GAS FROM LIQUID AT THE TOP OF THE VESSEL AND THEREBY INCREASE THE CIRCULATION RATE. SLOTS MAY ALSO BE CUT IN THE PARTITION TO INCREASE THE CIRCULATION RATE.

REACTION VESSEL HAVING INTERNAL RECYCLE MEANS 1971 D. A. CLAYDON ETA!- Filed Ma 5 Sheets-Sheet 1 INVIINI'OHS N o m v 5 ff AL 0 N LL 6 C a m Y T T NS m! 0 E H N ,y A T R M N E A 5 mm x VL .C A m w) D. A. CLAYDON ETAL 3,552,934

PJZAG'I'ION VESSEL HAVING INTERNAL RECYCLE MEANS 5 Sheets-Sheet 2 Filed May 2, 1968 cu RVOE a CURVE A O .I III HEIGHT OF FOAM ABOVE TUBE TOP-INCHES INVEN'I'ORS DAVID ANTHONY CLAYDON BY JULIUS ERNEST ELLIS %QC4 fl4/% 3WM ATTORNEYS REACTION VESSEL HAVING INTERNAL RECYCLE MEANS Filed May 2, 1968 5, D. A. CLAYDON ETAL 5 Sheets-Sheet 3 FIG. 6

CURVE B CU RVE A BoEw HEIGHT OF FOAM ABOVE TUBE-INCHES INVI'INIORS DAVID ANTHONY CLAYDON JULIUS ERNEST ELLIS ATTORNEYS D. A. CLAYDON REACTION VESSEL HAVING INTERNAL RECYCLE MEANS Filed May 2 1968 5 Sheets-Sheet 4 FIG. 7

o. /15 11mm 3A azuvm swuv'lnoulo FOAM HEIGHT ABOVE TOP OF INTERNAL BAFFLES IN CFIUCIFORM ARMS- INCHES DAVID ANTHONY CLAYDON JULIUS ERNEST ELLIS ATTORNEYS Jan. 5, 1971 D CLAYDON ET AL 3,552,934

REACTION VESSEL HAVING INTERNAL RECYCLE MEANS Fi1ed May 2, 1968 5 Sheets-Sheet 5 m m LU I 3 LLI CD D o '2 I, LIJ I o H. O O $0 I 1 g Z (I) 8 s O v 2 O t g 0 m K 0 in K o a N 9 x O Q LL 0 2 2 o H) N /15 wumowzm HELLVM awn/moan INVI'IN'IORS DAVID ANTHONY CLAYDON JULIUS ERNEST ELLIS ATTORNEYS FIG. 5

U.S. Cl. 23285 8 Claims ABSTRACT OF THE DISCLOSURE A reaction vessel which is a vessel divided by a partition into two zones which intercommunicate above and below the partition. Gas is introduced into the lower part of one of the zones to create a density difference between the liquid contents of the two zones and cause the liquid to circulate. The partition has a head which is a plurality of channels projecting into one of the zones, to assist in separation of gas from liquid at the top of the vessel and thereby increase the circulation rate. Slots may also be cut in the partition to increase the circulation rate.

The present invention relates to reaction vessels, and in particular to reaction vessels in which a liquid phase is caused to circulate as a result of a density diiferential set up by the introduction of a gaseous phase.

Reaction vessels of this type include two vertical zones connected at the top and at the bottom. A gas, which may or may not constitute one of the reactants, is introduced ino the liquid phase in a finely dispersed state at the bottom of one of the zones. The introduction of the gaseous phase causes a difierence in density between the liquid contents of the two zones with the result that circulation takes place, the direction of flow being upwards in the zone into which the gas is fed and downwards in the other zone. In the specification the two zones are referred to as the zone of liquid upfiow, and the zone of liquid downflow, respectively. At the top of the reaction vessel the gas separates from the liquid and is released from the reaction vessel. The circulation of the vessel contents ensures adequate heat transfer and mixing of the reactants. Reaction vessels of this type can be employed when the provision of mechanical means of agitation is undesirable, for instance where the reaction mixture is corrosive or where the reactor is operated under increased pressures.

In most reaction vessels of this type there is an incomplete separation of gas from the liquid at the top of the reaction vessel, so that the gas bubbles are carried down into the zone of liquid downfiow. As a result the difference in density between the liquid contents of the two zones is small, and a high circulation rate may not be achieved.

It is an object of the present invention to provide an improved reaction vessel of the type described in which improved separation of the gas from the liquid takes place at the top of the reaction vessel, and in which substantially increased circulation rates are obtained.

Accordingly the invention is a reaction vessel which is a vessel enclosing a partition which divides the vessel into two zones which intercommunicate above and below the partition and means for introducing gas in a finely divided state into the lower part of one of the zones to cause liquid to circulate between the two zones, wherein the partition has a head which is a plurality of openended channels projecting into one of the zones of the vessel.

United States Patent The head may be integral with the partition or it may be a separate member which is attached to the top of the partition by any suitable means; for example if the partition takes the form of a tube, it may slot into the top of the tube.

In a preferred embodiment of the invention, the partition is a tube and the head is cruciform shaped, having four channels.

Vertical baflles may be situated in the channels of the head, intermediate between the two ends of the channel.

The walls of the channel may be extended upwards. When the partition takes the form of a tube, the height of the walls may suitably be between /2 and 15 times the diameter of the tube, but this is not critical. The walls may be closed at their upper end at the end of the channel, provided that the lower portion of the channel is openended. This is illustrated in FIG. 3.

Slots may be present in the partition, below the head, as this increases the circulation rate. A shield may be placed adjacent to the slots in the zone of liquid upflow, as it is found that this also increases the circulation rate.

The partition may divide the vessel into two unequal volumes. In this case it is preferred to introduce gas into the larger of these volumes.

Reactors of the type described are suitable for use, for example, in the liquid phase oxidation of hydrocarbons with molecular oxygen to give acids.

One embodiment of the invention is shown in the accompanying diagrammatic drawings.

FIG. 1 shows a cylindrical reaction vessel 1 which encloses a concentric tube 2, supported by sets of arms 3 and 4. A ring 5 is connected to a source of supply of gasand has a series of nozzles situated at intervals around the ring via which gas in a finely divided state may be admitted to the reactor. A cruciform shaped head '6, is situated on top of the tube 2, which divides the reactor vessel into a zone of liquid upfiow, between the outer wall of the tube and the inner wall of the reactor, and a zone of liquid downflow inside the tube 2. An exit 7 is provided at the top of the vessel for removal of gases from the reactor. A Pitot tube 8, connected to a manometer 9, is situated insidethe tube 2, to enable the rate of flow of liquid inside the tube to be measured. The Pitot tube and manometer are present to enable measurements of circulation rate to be carried out and are not normally present.

FIG. 2 shows more clearly the cruciform shaped head 6, and shows the skirt open at the ends of each channel of the cruciform.

FIG. 3 shows a second head according to the invention in which the walls of the channels are extended upwards and are closed at their upper ends, but the actual channel is open-ended, and vertical baflles 10 are provided in each channel.

FIG. 4 shows a tube and head according to the invention in which slots 11, are provided in the tube below the head and a shield 12 is situated adjacent to the slots.

FIGS. 5-8 show, graphically, the increased performance resulting from the use of the inventive recycle means.

EXAMPLE 1 A tubular reactor of the type shown in FIG. 1, but having no cruciform shaped head 6, had an internal diameter of 6 in. and was fitted with a plain central vertical tube 2 in. inside diameter and 45.5 in. high which divided it into zones of liquid upfiow and downfiow. The liquid was water and air was admitted via the sparger. The velocity of the circulating water passing through the zone of liquid downfiow was measured by means of the Pitot tube. The results are shown in curve A of FIG. 5 as a graph of water velocity versus height of the foam above the top of the internal tube.

This procedure Was repeated but on top of the central vertical tube a cruciform head 6, as shown in FIG. 2, was inserted. The head had four channels A in. wide, 1 /2 in. long and 16 in. high made from thin aluminium sheet. Each channel extended to about /2 in. from the reactor wall. The bottom of each channel was closed so that froth could therefore only enter from the region adjacent to the wall of the reactor. The results are shown in curve B of FIG. as a graph of circulating water velocity versus height of foam above the floor of the channels which were at the same level as the top of the internal tube.

It can be clearly seen that the use of a cruciform baflie gives a considerable increase in the circulating water velocity at foam heights above the top of the central tube greater than 4 in.

EXAMPLE 2 The experiments with the apparatus described in Example 1 above were repeated using air and a 0.03% solution of hexylene glycol in water. This solution gave a foam of higher aeration than water alone and on this account was thought to be more typical of the foam found in some reacting systems. The results are shown in FIG. 6 plotted in the same way as in Example 1. Again it is seen clearly the velocities obtained with the cruciform baflle (curve B) are considerably greater than those obtained with the plain tube (curve A).

EXAMPLE 3 The reactor of Example 1 was used. On top of the central vertical tube a cruciform head 6, was fitted. The head had four channels in. wide, 2 in. long and 24 in. high, made from thin aluminium sheet. The bottom of each channel was closed but a portion of each arm 4 in. high and /2 in. Wide was cut away at the bottom as shown on FIG. 3. Midway along each arm a baffie 9 in. high extended from the floor of the channel as shown on FIG. 3.

The liquid was water and air was admitted via the sparger. The velocity of the circulating water passing through the zone of liquid downflow, the central tube, was measured as before by means of a Pitot tube. The results are shown in FIG. 7 as a graph of Water velocity versus height of the foam above the top of the internal baffles in the channels of the cruciform. On comparing FIG. 7 with FIG. 5 it will be seen that the introduction of slots and internal baffles to the cruciform head has given a significant measure in the water circulation over that obtainable by the simple cruciform design of FIG. 2. (Compare curve B of FIG. 5 and FIG. 7.)

EXAMPLE 4 The reactor of Example 1 was used. On top of the central vertical tube a cruciform head was fitted. The baflle was of similar design to that described in Example 3 except that the overall height of the head was 15 in., the slot cut away at the base of each channel was 3 in. high by /2 in. wide, and the internal baffles were 6 in. high. 16 in. down from the top of the central tube four equally spaced slots, 8 in. high and /2 in. wide, were cut in the tube wall as shown in FIG. 7. These slots were roughly half way along the length of the central tube and they were placed so as to be out of phase with the channels of the cruciform head as shown. These slots were shielded from direct access of the foam outside the central tube by a circular shield situated /2 in. away from the slots. The foam could reach the slots by passage around the top and bottom of the shield.

The liquid was water and air was admitted via the sparger. The water velocities measured by the Pitot tube at the base of the zone of liquid downflow are shown on FIG. 8 plotted against the height of the foam above the base of the slots cut in the wall of the central tube. It will be seen that the highest velocity obtained with the cruciform bafile and the shielded slots in the central tube wall is greater than any velocity found in Examples 1 and 3.

We claim:

1. A reaction vessel which is a normally vertical vessel enclosing a vertically extending draft tube which divides the vessel into a liquid upfiow zone and a liquid downflow zone which intercommunicate above and below the draft tube, means for introducing gas in a finely divided state into the lower part of the liquid upfiow zone to cause liquid to circulate between the two zones, and a head at the top of said draft tube having a plurality of open-ended channels projecting into the liquid upfiow zone for disengaging gas from an upflowing mixture of gas and liquid, said channels providing communication between said liquid upfiow and liquid downflow zones through said open ends, said head having an outer diameter larger than the outer diameter of said draft tube.

2. A reaction vessel according to claim 1 wherein vertical battles are situated in the channels of the head, intermediate the two ends of the channel.

3. A reaction vessel according to claim 1 wherein the draft tube divides the vessel into two unequal volumes and gas is introduced into the larger of these volumes.

4. A reaction vessel according to claim 1 wherein slots are present in the draft tube below the head.

5. A reaction vessel according to claim 4 wherein a shield is placed adjacent to the slots in the zone of liquid upfiow.

6. A reaction vessel according to claim 1 wherein the draft tube is centrally located in the reaction vessel.

7. A reaction vessel according to claim 6 wherein the head is cruciform shaped.

8. A reaction vessel according to claim 6 wherein the height of the walls of the channel is between /2 and 15 times the diameter of the tube.

References Cited UNITED STATES PATENTS 2,597,802 5/1952 Kappe 210-197 3,065,061 11/1962 Fett 23-283 3,243,169 3/1966 Candle et a1. 26l--123X 3,305,444 5/1968 Dufoumet 210197X FOREIGN PATENTS 612,005 4/1935 Germany 261123 620,043 3/1949 Great Britain 23285 MORRIS O. WOLK, Primary Examiner B. S. RICHMAN, Assistant Examiner US. 01. X.R. 23283 210197; 261 -36, 123 

